In imaging devices, the images or video sequences captured by such devices are often susceptible to quality degradation due to inadvertent shaking of the devices during image capture. In video capture, shaking of the imaging device can result in undesirable motion or jitter in the captured video sequence. In still image capture, the shaking may result in blurring of the captured image. Blurring or jitter can make it difficult for the human visual system to focus and concentrate on a region or object of interest within the image. In either case, the quality of the viewing experience of the video or image is reduced.
Image registration techniques can be used to compensate for inadvertent shaking to produce better image quality. Image registration systems generally fall into three main categories: optical image stabilizers (OIS), mechanical image stabilizers (MIS), and electronic image stabilizers (EIS). OIS systems employ an adjustable lens that morphs the image before it reaches the sensor to reduce the effect of shaking. MIS systems stabilize the entire camera, e.g., using the center of gravity of the camera, a counterbalance system, and/or the camera operator's body to minimize shaking. EIS systems employ signal processing algorithms to alter the captured images and thereby address the effects of shaking. In some image processing applications, image registration may also be used to fuse a short sequence of images into one picture. EIS systems may be less expensive to implement than OIS and MIS systems, and may be preferred over OIS and MIS systems for devices such as wireless radio telephone handsets equipped with imaging capabilities, e.g., so-called camera phones.
For video capture, imaging devices may implement block-based video compression techniques, such as those defined by the MPEG-2, MPEG-4, ITU-T H.261, H.263, or H.264/MPEG-4, Part 10, Advanced Video Coding (AVC) standards. Video compression techniques perform spatial and temporal prediction to reduce or remove redundancy inherent in video sequences. Motion estimation and motion compensation, for example, are common and effective block-based video coding techniques used to remove temporal redundancy in a coded video sequence, and thereby achieve data compression.